1. Field of the Invention
This invention relates to thermal containers, and more particularly to an advanced thermal container for shipping that uses a highly efficient thermal seal and high quality thermal insulation to minimize the exchange of heat and air between the interior and exterior of the container. The advanced thermal container also incorporates a built-in data monitoring system.
2. Description of Prior Art
A wide variety of insulated containers are currently used for shipping temperature sensitive products. Those containers use different types of insulation and refrigeration to maintain a desired thermal environment within the container. A typical prior art thermal shipping container designed to maintain cool temperatures is a polystyrene plastic box with ice or a frozen gelpack inside the box's payload region. A significant problem with this approach is the heat flux through the box walls and the interface between the box and its closing member. Depending on the thermal resistivity of the insulation and the ambient temperature outside the box, the heat leak into the box can be significant. The resulting heat load typically must be convectively carried to the heat reservoir to maintain constant temperature within the box.
Note a similar problem exists in reverse if a hot product is the payload and a heat source such as a hot brick is the heat reservoir. Everything stated below will be limited to the cold payload situation, but the present invention is not limited to that.
Prior art insulated containers have proved unsuitable for products that require tight temperature tolerances. Excessive heat gain can exhaust the heat reservoir, causing the temperature to rise rapidly with additional heat gain. Temperature variation can exceed tolerances because the heat reservoir may absorb too much heat from the product itself, lowering its temperature to an unacceptable level. The temperature gradient within the payload volume may be unacceptably large because the warmer air that accumulates near the top of the container is somewhat removed from the colder air surrounding the heat reservoir lying on the bottom of the box. Depending on the extent of temperature gradient, a payload could conceivably be too cold at the lower end and too warm on the upper end.
Another deficiency of prior art insulated shipping containers involves the recordation, transmission, and reception of data and other information, such as temperature data or computer program instructions. Many data monitoring systems are not integral to the box and sensors are placed in the box wherever they and the payload can be accommodated. In many cases this violates shipping requirements mandating that the warmest location in the box be monitored. Different boxes have different warmest locations and portable sensors often are incorrectly placed for a particular box. Portable monitors also require an adjustment period after being initially placed in the box before they can provide accurate data. Thus, at the critical time of initial loading of the payload, when the monitor is simultaneously placed in the box, accurate monitoring is not possible.